Device and method for handling substrates by means of a self-leveling vacuum system in epitaxial induction

ABSTRACT

A device for handling substrates, used in an epitaxial apparatus or reactor ( 20 ) for chemical vapour deposition (CVD) onto the said substrates, comprises an internal robot ( 30 ) provided with means ( 60 ) for gripping and transporting substrates, which are in the form of semiconductor slices ( 24 ), in order to transfer them from cassettes ( 38, 40 ) containing the semiconductor slices ( 24 ) to be processed, the gripping and transportation means ( 60 ) having precisely the task of transporting the slices ( 24 ), which are present in a purging chamber ( 34 ) and supplied from a cassette ( 38 ) for storage of the said slices ( 24 ), from the purging chamber ( 34 ) into a reaction chamber ( 22 ) of the epitaxial reactor ( 20 ) and, more particularly, into seats ( 28   a-e ) formed on a flat disk-shaped susceptor ( 26 ) which is present in the reaction chamber ( 22 ) of the epitaxial reactor ( 20 ) and vice versa, from the reaction chamber ( 22 ) again passing through the purging chamber ( 34 ), to the cassettes ( 38, 40 ).

The present invention relates to a device for handling substrates, inparticular semiconductor slices, in an apparatus used for the chemicalvapour deposition (CVD) of semiconductor material onto the saidsubstrates and a method for operation of the said device. It especiallyrelates to a device for handling substrates used in an epitaxial reactorand, in particular, relates to an epitaxial reactor for performing thechemical vapour deposition (CVD) of materials onto the said substrates,preferably silicon substrates used in the manufacture of semiconductorcomponents, such as chips for integrated circuits.

More particularly, the present invention relates to a device used inepitaxial reactors such as those covered by the International PatentApplication WO 96/10659 filed on Sep. 14, 1995, with the title“Epitaxial reactor provided with flat disk-shaped susceptor and having agas flow parallel to the substrates”. With the aid of the presentdevice, the abovementioned epitaxial reactor becomes a reactor of the“cassette-to-cassette” type because the cassettes containing the as yetunprocessed substrates are positioned inside the reactor and, during aproduct loading cycle, a first mechanized arm, or robot, not formingpart of the present invention, is used to transport the substrates froma storage rack or “cassette” to a purging chamber and a secondmechanized arm, or robot, carrying externally a gripping andtransportation means, forming the subject of the present invention, fortransporting the substrates from the purging chamber to the susceptor,whereas, during an unloading cycle, the second robot transports thesubstrates from the susceptor to the purging chamber and subsequentlythe first robot transports the said substrates, which have undergoneprocessing, from the purging chamber to one of the cassettes, all ofwhich occurring without manual intervention of an operator supervisingoperation of the reactor.

The invention may be applied in particular to cold-wall CVD systems,preferably, to reactors which are able to provide epitaxial growth onsubstrates or silicon slices which are used in the manufacture ofsemiconductor devices by means of deposition involving chlorosilanevapour pyrolysis.

The commercially most widespread epitaxial reactors can be divided intotwo main categories:

a) single-slice reactors, which are able to process a single slice at atime; and

b) batch-type reactors, which are able to process a plurality ofsubstrates or slices at the same time.

The heating systems used for the abovementioned reactors may beclassified as two types: lamp-type heating systems and medium or highfrequency induction heating systems.

The batch-type reactors which are most widespread on an industrial levelare essentially of two types: those which use the so-called “barrel”system, i.e. with a prismatic or truncated-pyramid susceptor, and thosewhich use the “pancake” system, with a substantially flat disk-shapedsusceptor.

Typically, at present, batch-type reactors are of the manual loadingtype, whereas single-slice reactors are of the automatic loading type.

In automatic-loading reactors, the substrate, or slice, may be handledin different ways which offer both advantages and disadvantages.Handling of the substrates is particularly critical in the sector ofsemiconductors and, in particular, in epitaxial reactors where there aretemperature-related problems and problems resulting from particlecontamination.

Generally, each substrate or slice has a bottom side (back), a top side(front) and a side wall (edge). The dimensions of the front and back arenormally between 75 and 300 mm, and even as much as 400 mm, while thedimensions of the edge are smaller than or near to 1 mm. The front isthe most important part of a slice because it is the part where thechemical reaction process, i.e. deposition, takes place.

For the abovementioned reason, it is important to avoid all contactbetween the front and any type of tool used for handling, because anycontact, even of the slightest nature, causes imperfections in thecrystal lattice. If the imperfections are formed during loading, theyare magnified by the ensuing heat process; however, imperfectionsintroduced during unloading must also be avoided.

Basically, it may be stated that contact, even of an accidental nature,with the front of the slice is nor permitted at any time. On the otherhand, within certain limits, contact with the back and with the edge ofthe said slice is permitted.

Therefore, in order to move a slice, it is possible to act via the front(without any direct contact, however), the back or the edge.

Basically, there is only one system which allows handling from thefront, without contact between tool and slice, and it is the systembased on the Bernouilli effect, whereby, by providing a suitablegripping tool (end effector), it is possible, by blowing filtered inertgas, towards the front of the slice, to create an attraction effect forthe slice, which, in the horizontal position, is sufficient to overcomethe weight of the slice, keeping it suspended.

However, accidental contact between the edges of the slices and somefixed points of the tool necessarily occurs because, in the absence of asupport and hence friction, it is necessary to have some fixed pointsfor fixing the slice underneath the gripping tool, although this fact isnot particularly negative.

During unloading, in order to raise the slice from the cavity insidewhich it is seated, it is necessary to overcome, in addition to its ownweight, also a slight vacuum which is formed between the cavity and thesaid slice. Since this is not possible by means of the Bernouilli effectalone, it is necessary to avoid the formation of this vacuum, forexample by means of a network of tiny channels which are formed in thecavity underneath the slice. This technique is excellent, but is bettersuited for lamp-heated reactors, rather than induction-heated reactors,because the presence of non-conducting channels in the graphite mass ofthe susceptors would adversely affect the uniformity of heating of theslices. Moreover, this technique is not particularly compatible withreactors of the batch type because, although a flow of inert gas helpsin keeping the front of the slice clean during handling, it is probablyharmful for the adjacent slices, especially if handling takes place inthe vicinity if the susceptor, because the flow of gas moves any dustparticles which are present in movement.

Another system consists in handling the slices from the back, althoughthere is the problem that the back of the slice is accessible when thelatter is inside the cassette, but is no longer so when the slice islocated on the susceptor. In order to overcome this drawback, it ispossible to form through-holes in the susceptor and raise the slice,when required, by means of small supports, passing through the holes,which are able to move up to perform raising and move down to allowseating of the slice in the susceptor. In fact, during the loadingcycle, the supports are raised and the slices rested on them. Then thesupports are lowered and the slices are deposited in the correspondingseats on the susceptor. During the unloading cycle, the supports areraised, together with the slices; a tongue or gripping tool (endeffector) made of suitable material is then introduced underneath theslice and the latter removed. If greater stability is required, it ispossible to brake the slice by applying a slight vacuum between sliceand gripping tool. However, this technique, although being effective, inpractice can only be properly applied to reactors of the lamp-heatedtype, while it is probably unacceptable for induction-heated reactorsbecause the holes formed in the graphite of the susceptor would resultin a non-uniform current flow and hence heating.

Another known system is that which allows the slice to be gripped alongits external diameter, or edge, at two or more points using movablegripping systems, such as mechanical grippers. However, this systemcannot be easily realized, since it requires special machining of thecavity or the cavities of the susceptor which are not entirelycompatible with the induction heating system. Finally, as alreadymentioned, any direct contact with the front of the slice is notpermissible.

There exist, however, systems which are able to perform gripping of theslice from the front, limiting the contact to one or more areas on itsexternal rim.

The slice is retained by a vacuum system by means of a chamber formedbetween slice and gripping tool. In this case, however, the raisingforce is limited to the surface area of contact with the external rim ofthe slice and an even slightest error in positioning between slice andgripping tool results, respectively, in a smaller or greater contactsurface area with risks of lack of gripping of the slice or an increasein defects due to the direct contact between tool and slice. By way ofconclusion, this system is not of an optimal nature owing to anexcessively large contact surface area between tool and front of theslice.

The object of the present invention is that of providing an improvedautomatable device for supplying and removing semiconductor slicesto/from an epitaxial reactor such as that described in the saidInternational Patent Application WO 96/10659 which covers an epitaxialreactor provided with a flat disk-shaped susceptor and having a gas flowparallel to the substrates.

In short, operation of the reactor and the associated device comprisesthe following steps:

positioning racks or cassettes containing the slices to be grown insidethe reactor,

loading of the product, where the slices are transferred inside thereaction chamber, as described in greater detail below;

brief hydrogen purging inside the reaction chamber;

heating so as to bring the susceptor and the slices up to theappropriate temperature;

processing cycle as required by the relevant specification;

cooling to a temperature compatible with the unloading step; and

unloading of the grown slices and transportation back into thecassettes, as described in greater detail below.

The loading and unloading steps are performed at temperatures which arecompatible with the material forming the gripping tool.

Each growing cycle may be followed by other growing cycles or by aso-called etching cycle where the slices are not loaded and thefollowing operations are performed:

brief purging by means of hydrogen in the reaction chamber;

heating so as to bring the susceptor up to the appropriate etchingtemperature;

etching cycle as required by the relevant specification; and

cooling to a temperature compatible with loading of slices following theetching step.

The epitaxial reactor forming the subject of the abovementionedInternational Patent Applciation WO 96/10659 is of the so-called“pancake” type, namely with a disk-shaped susceptor which isinduction-heated, so that none of the systems illustrated hereinabovemay be effectively used.

In order to overcome the abovementioned drawbacks, a solution is used,comprising:

a first reactor zone, towards the so-called clean room, intended toreceive the cassettes containing the slices to be processed and thosealready processed, where this part of the reactor may be in an airatmosphere or, alternatively, may envisage a chamber for purging with aninert gas, at least at the ambient temperature for the silicon of theslice to be processed (an inert gas, even low-cost such as nitrogen, maybe preferable to air). Below the more simple case of an air atmosphereis described, where neither particularly efficient gas seals norprolonged washing with inert gases is required. In the case where air isused, only a so-called absolute filter for the air is added in order tokeep the air atmosphere as free as possible from solid particles (dust).Moreover, the same first zone of the reactor is provided with two doorswhich can be opened at any time, so as to allow the removal of thecassettes containing the slices, where opening of the doors does notrequire particularly long purging or washing cycles with inert gases.However, by way of alternative, should processing of the slices makeunacceptable even the smallest defects due to local oxidation of thesaid slice, the first zone of the reactor may be provided with sealeddoors and a system for purging, also by means of a pneumatic extractionpump, and introduction of inert gas, in order to minimize exposure ofthe slice to the air and consequently the said defects. A first robot,called external robot controlling handling of the slices, exists, theslices being handled from the back since the present cassettes which arecommercially available are constructed precisely to allow this type ofhandling. A gripping tool of the external robot, which is alsocommercially available, transports the slices, keeping them pressed inposition by means of a small vacuum source which is available in therobot.

The operating principle of the abovementioned solution is explainedhereinbelow.

During loading, a slice is removed from the corresponding cassette andis positioned in an alignment and centring station which may also beconstructed inside the said external robot. The cassettes, the alignmentand centring station and the external robot are not novel and do notform part of the present invention.

Here the slice is oriented at the desired angle and the position of itsgeometric centre is calculated so as to allow subsequent precisegripping. The slice is then positioned inside the purging chamber on topof a quartz disk which acts as a support and is shaped so as to allowhandling by means of the commercial gripping tool of the said externalrobot. The quartz disk has a relatively large mass compared to the sliceso as to dissipate better its heat during unloading.

The access door is closed and the purging chamber is washed with aninert gas, in order to remove completely every trace of air, and, ifnecessary, washing may be aided by a vacuum extraction cycle in order toaccelerate the said purging operation. At this point, the door providingaccess to the chamber where the internal robot according to theinvention operates is opened, said chamber operating always in aninert-gas atmosphere and, except during maintenance operations, neverbeing exposed to the air.

The gripping tool, or hand, of the internal robot forms part of thepresent invention, which invention allows the slices to be suitablyhandled by means of a very limited contact with their edges. In fact,each slice has a chamfered part or edge extending over about 1 mm. Thepart of the gripping tool in contact with the edge of the slice isshaped so as to limit the contact zone to the sole chamfer of the edge,extending over about 1 mm, and is made of suitable material, such asquartz. This part of the slice is not, however, useful in themanufacture of integrated circuits and therefore this solution is notdamaging for the quality of the finished product. Moreover, the grippingtool, or hand, is connected to the arm of the internal robot by means ofa structural pipe which has two functions:

the first is that of extending the robot arm so as to reach the positionof the susceptor inside the reaction chamber;

the second is that of achieving, by means of an articulation or byexploiting the flexibility the arm, a certain degree of self-levellingbetween tool, or hand, and slice which is used during the operationsinvolving raising of the said slice.

Raising of the slice is ensured by a certain vacuum which is obtained bya dedicated pneumatic machine. The vacuum is transferred to the slice bymeans of a series of holes which are distributed along the periphery ofthe gripping tool and are concentrated in the round zone of the sliceand absent in a flat zone or recessed notch zone which is used foridentification and orientation of each slice, where the flat zone ispreferred for slices with a diameter of up to 150 mm, whereas in thecase of larger-diameter slices the recessed notch zone is preferred.Since every irregularity in the shape of the slice causes a localreduction in the effects of the vacuum, according to the invention it isnecessary to offset this reduction with a suitably calculatedconcentration of suction holes in the gripping tool.

During loading, the susceptor rotates and correctly positions, by meansof reference systems known per se, the cavity to be loaded. Thispositioning may be performed by means of optical systems which are knownper se. Then the slice is introduced into the reaction chamber andpositioned above a suitable cavity of the susceptor. The internal robotmoves downwards slightly, brings the slice into contact with the cavityand, when the vacuum is removed, releases the slice which is loaded ontothe said cavity. The loading steps are repeated until all the cavitiespresent on the susceptor are occupied. The scheduled processing of theslices is then started.

Out of all the optical systems it is possible to use a laser telemetersystem which measures the distance between a laser emitter and thesusceptor in question, producing an analog signal which is proportionalto the said distance. For example, the laser telemeter helps eliminatedefects in the parallel positioning of the susceptor by means of ascanning algorithm and subsequent correction by mechanical means whichare known per se (for example micrometer screws). This parallelpositioning is essential for ensuring uniformity of the epitaxialdepositions onto the slices.

Once the scheduled processing of the slices has been completed, it isnecessary to unload them from the susceptor. To do this, after waitingfor the susceptor to reach a suitable temperature allowing extraction,without damage, of the slices from the reaction chamber, it is necessaryto use again the said internal robot, which removes each slice from thecorresponding cavity of the susceptor and transports it inside thepurging chamber where it is placed onto the quartz disk which, with itslarge mass, cools it. After sufficient cooling, the slice is transferredby the external robot to a seat of one of the cassettes located in thefirst zone of the reactor.

The present invention which implements the methods described aboveconsists in a device for handling substrates of materials produced inepitaxial apparatuses or reactors, such as slices of semiconductormaterials, comprising:

a reaction chamber,

an internal robot for handling the substrates or slices of semiconductormaterials,

a purging chamber for passing the slices through a cleaning atmosphere,

a storage zone containing cassettes which house, in a stackedarrangement, the slices of semiconductor materials,

an external robot for transferring the slices from the store to thepurging chamber,

the internal robot comprising a sealed chamber which houses anarticulated arm having a gripping means at its external end,

characterized in that the gripping means of the internal robot comprisesat least one arm which can be inserted into the reaction chamber andterminating in a gripping tool or hand for removing a slice ofsemiconductor material from the purging chamber and transporting it,after passing through the sealed chamber, so as to be deposited in arecessed seat of a disk-shaped susceptor of the reaction chamber, andvice versa, from the recessed seat to the purging chamber, where thehand is designed to contact the slice on its uppermost surface along aperipheral zone or chamfered edge and the hand is adapted to grip theslice by means of a vacuum effect, and where the gripping means includesmeans for attaching it pivotally to the articulated arm in such a mannerthat when depositing the substrate in the recessed seat the substrate isheld inclined to the plane of the recessed seat so as to touch therecessed seat initially only with the slice edge located farthest fromthe arm of the gripping means before then pivoting about said edgetouching the seat to become fully in contact therewith, and vice versa,when transporting a slice from the reaction chamber to the purgingchamber, the slice gripped by the hand's vacuum effect is detached fromthe recessed seat by first lifting the side of the slice nearest the armof the gripping means and then detaching the substrate completely, andraising the substrate further whilst being held inclined to the plane ofthe recessed seat.

In particular the arm is tubular and hollow, being connected, on oneside, by means of a flexible pipe to a vacuum source and, on the otherside, to a circular seat formed inside the hand so as to apply a vacuumbetween a bottom side of the said hand and a slice present underneaththe hand.

Preferably, articulation means are arranged between the hollow tubulararm and the articulated arm of the internal robot, said means allowingthe hollow tubular arm to be raised and lowered so as to bring the handabove and below a plane defined by the articulated arm.

In addition, articulation means are arranged between the hollow tubulararm and the articulated arm of the internal robot, said means alsoallowing a rotation of the hollow tubular arm about its longitudinalaxis.

Preferably, the articulation means comprise a support bearing which isfixed to the articulated arm and carries a rotating pin about which thearticulation means rotate, and an adjusting screw for fixing thepermitted heights for raising and lowering of the hand with respect tothe plane of the articulated arm, so that the hand can rest in theradial direction on the disk-shaped susceptor only with the front part,only with the rear part or perfectly level with the said susceptor.

In addition, the articulation means also comprise, around the hollowtubular arm, anti-friction bushes for allowing alignment of the saidhand, in a direction perpendicular to the radius of the disk-shapedsusceptor.

Even more preferably, the hand is in the form of a disk with a diametergreater than the diameter of the slice to be handled and has a bottompart, facing the slice, provided with a recessed seat which engages onlywith an external peripheral rim of the said slice.

Preferably, the seat is present on a bottom part of the hand and isprovided with a plurality of peripheral holes connected to a chamberinside the said hand which, in turn, is connected to the hollow tubulararm so as to apply a vacuum between the slice and the hand.

Most preferably, the peripheral holes are concentrated mainly where thegreatest losses in vacuum are envisaged.

In a particular embodiment, a laser telemeter is used to measure adistance between a laser emitter and the disk-shaped susceptor of thereaction chamber, in question, producing an analogue signal proportionalto the said distance, where said telemeter detects defects in the levelarrangement of the susceptor as well as defects in the parallelpositioning of the susceptor with respect to the reaction chamber.

Furthermore, a notch formed in the external rim of the susceptor is usedas an angular reference point which can be detected by the lasertelemeter and the recessed seats for the slices are counted startingfrom this notch.

According to the present invention, a method for placing a slice in arecessed seat of a disk-shaped susceptor, present in a reaction chamber,by means of a hand of a device, as defined above, is also provided,characterized in that a slice, which is made to adhere to the hand bymeans of a vacuum, enters into the reaction chamber in the raisedposition, is transported to above one of the recessed seats of thedisk-shaped susceptor, is lowered so as to be placed onto the said seat,remaining inclined forwards so as to touch the recessed seat initiallyonly with the slice edge located farthest from the arm of the grippingmeans and then with its whole surface, and then, after removal of thevacuum which keeps the slice attached to the hand, is further lowered,detaching the hand from the slice, and then the hand is raised again,being detached entirely from the slice, and finally is retracted,leaving the reaction chamber.

Alternatively, the method for removing a slice from a recessed seat of adisk-shaped susceptor, present in a reaction chamber, by means of a handof a device, as defined above, is characterized in that the hand entersinto the reaction chamber in the raised position, is transported toabove a slice housed in one of the recessed seats of the disk-shapedsusceptor, is lowered until it touches the slice, first at the edgelocated farthest from the arm of the gripping means and then over theentire circumference of the slice and then, after touching the sliceover the entire circumference, applies a vacuum so as to cause the sliceto adhere with its edge onto the hand and then starts to move up again,detaching the slice from the recessed seat, first at the edge locatednearest the arm of the gripping means and then over the entire surfaceof the slice, and finally, after the slice has been raised completelyfrom the recessed seat of the susceptor, transports it outside thereaction chamber.

The features of the present invention will be defined in the claimsforming the conclusive part of the description thereof. However, otherfeatures and advantages will emerge from the following detaileddescription of an example of embodiment thereof, provided by way of anon-limiting example, in which:

FIG. 1 is a sectioned plan view of a disk-shaped epitaxial reactorserved by an external robot and an internal robot according to theinvention;

FIG. 2 is a sectioned and truncated side view of a gripping tool, orhand, situated at the end of an extendable arm of the internal robotaccording to the present invention;

FIG. 3 is a sectioned and truncated plan view of the said gripping tool,or hand;

FIG. 4 is a partial, sectioned and enlarged view of the detail of thehand, encircled in FIG. 2, intended to show how the hand engages withthe slice of semiconductor material to be transported;

FIGS. 5 to 8 are sectioned and truncated side views which show anapproach sequence, towards a cavity of the susceptor, of the grippingmeans of the internal robot carrying a semiconductor slice so as to loadthe slice in the cavity of the susceptor;

FIGS. 9 to 12 are sectioned and truncated side views which show asequence where the gripping means is detached from the slice loaded inthe cavity of the susceptor;

FIGS. 13 to 16 are sectioned and truncated side views which show anapproach sequence of the gripping means of the robot towards asemiconductor slice present in a cavity of the susceptor, in order toremove the said slice; and

FIGS. 17 to 20 are sectioned and truncated side views which show asequence where the semiconductor slice is detached and removed from thecavity of the susceptor.

Let us consider first of all FIG. 1 which shows an epitaxial reactor 20comprising a reaction chamber 22 served by several robots for placingand removing slices 24 _(a-e) of semiconductor material onto/from adisk-shaped susceptor provided with cavities 28 _(a-e) having dimensionsfor receiving the said slices 24 _(a-e).

Since the slices 24 _(a-e) must be placed in and removed from thecavities 28 _(a-e) of the disk 26 present in the reaction chamber 22without being manipulated manually, for this purpose a so-calledinternal robot 30 has been provided, said robot 30 comprising a tubulararm 64 terminating in a gripping tool or hand 70, forming the subject ofthe invention, and a so-called external robot 32. The internal robot 30remains localized between the reaction chamber 22 and a purging chamber34 having the function of processing slices 24 _(a-e) passing between afirst zone or storage zone 36 for slices and the internal robot 30 and,vice versa, from the internal robot 30 to the first storage zone 36.

The storage zone 36 is provided with two cassettes 38 and 40 which havethe function of containing slices of semiconductor material which are toundergo processing in the reaction chamber 22 or containing the slicesof semiconductor material which have undergone processing in thereaction chamber 22. Moreover the storage zone 36 contains anarticulated arm 42 terminating in a gripping means 44 of the vacuum typewhich has the function of ensuring transportation of slices 24 from thecassette 38 to the purging chamber 34 and, vice versa, from the purgingchamber 34 to the cassette 40. The articulated arm 42 is already knownper se.

The purging chamber 34 comprises a first hermetically sealed door 50 ofthe rapid-action type, such as a guillotine door, a second hermeticallysealed door 52, of the same type as the door 50, and a disk 54 forsupporting the slices 24 passing through into the said purging chamber34. Preferably, the disk 54 is made of quartz so as to ensure goodwear-resistance and substantially zero contamination and is providedwith a recess 55 for receiving the gripping means 44 when it enters intothe purging chamber 34 in order to deposit or remove a slice 24. Thedisk 54 has a relatively large mass, compared to the slice, in order todissipate better its heat during the cooling stage. The purging chamber34 has the function of preparing the slices 24 to pass from thesubstantially dust-free atmosphere of the storage zone 36, which may beair or another simple inert gas, such as nitrogen, to that of thereaction chamber 22, which consists mainly of hydrogen, and vice versa,from the atmosphere of the reaction chamber 22 consisting essentially ofhydrogen to that of the storage zone 26, since it is desirable to avoidintroducing gases which react with hydrogen into the reaction chamberand releasing into the atmosphere the hydrogen and gases which areformed in the reaction chamber during the CVD operations and which maybe poisonous or an irritant, such as HClI for example.

The internal robot 30 is contained in a sealed chamber 56 provided, inaddition to the hermetically sealed door 52 communicating with thepurging chamber 34, also with another hermetically sealed door 57communicating with the reaction chamber 22 and comprises an articulatedarm 58 which has at its external end a gripping and transportation means60, which will be described in greater detail in FIGS. 2 to 4 and whichhas the function of transporting the slices 24 from the purging chamber34 to the reaction chamber 22 and vice versa.

If we consider FIGS. 2 to 4, it can be seen that a gripping andtransportation means 60 according to the present invention consists ofarticulation means 62, which are connected to the articulated arm 58, atubular arm 64 provided with a connection piece 66 for connection to aflexible pipe 68 (visible in FIG. 1) which, in turn, is connected to apneumatic machine (not shown) as a vacuum source. The tubular arm 64 isconnected, at its end remote from the articulation means 62, to agripping tool or “hand” 70 which has the function of retaining a slice24 during its transportation from the slice support disk 54 present inthe purging chamber 34 to the disk-shaped susceptor 26 and, vice versa,from the susceptor 26 to the support disk 24.

The hand 70 is formed by two components 72 and 74 in the shape of acircular rim and bonded together. The top component 72 is provided witha tail-piece 76 for securing to a clamp 78 connected to the tubular arm64 and forms, together with a tail-piece 80 of the bottom component 74,a duct 82 communicating with the tubular arm 64. The bottom component 74is provided with a circular cavity 84 communicating with the duct 82 andwith small holes 86 _(a-m) passing through its side directed towards theslice 24. Moreover, this bottom component 74 enters into contact onlywith a limited edge portion 25 of the slice 24 which is envisaged ashaving no useful function for the processing to be performed on theslice.

Let us now consider FIGS. 5 to 8 which depict the procedure with whichthe gripping means 60 deposit a semiconductor slice 24 inside a cavity28 of the susceptor disk 26. As has been amply depicted in FIGS. 2 and3, the gripping means 60 is formed by a hand 70 which is connected bymeans of the tubular arm 64 and the connection piece 66 to a flexiblepipe 68 communicating, upon actuation, with a vacuum source.

As shown in FIG. 5, the gripping means 60 enters into the reactionchamber 72, transporting a semiconductor slice 24 adhering to the hand70, where adhesion of the slice 24 to the hand 70 is ensured by thevacuum (symbolically shown by an arrow 90) applied to the connectionpiece 66. Entry into the reaction chamber 22 is symbolically shown by afirst bold arrow 92 which indicates a forwards movement of thearticulated arm 58. Then the gripping means 60 starts to move downwardstowards the disk-shaped susceptor 26, as symbolically shown by a secondbold arrow 94 which indicates a downward movement of the saidarticulated arm 58.

For as long as the articulated arm 58 is raised such that the slice 24held by the hand 70 does not touch the cavity 28 on the disk-shapedsusceptor 26, the weight of the hand 70 and the slice 24 causes thearticulation means 62 to rest on a pad 96 present at the end of the arm58, rotating about a pivot pin 98 and descending as far as a pointpermitted by an adjusting screw 100. When the arm 58 moves downwards tothe point where the end of the slice 24 touches the cavity 28 locatedtowards the inside of the susceptor 26, as can be seen in FIG. 6, thedownward movement of the hand 70 stops and the gripping means 60 isoriented increasingly parallel to the susceptor 26 with the start ofraising of the screw 100 until, as can be seen in FIG. 7, the slice 24rests totally on the cavity 28. At this point the vacuum, represented bythe arrow 90, is removed, causing the slice 24 to be detached from thehand 70. In the meantime, before the slice 24 has become detached fromthe hand 70, two bushes 63 and 65 made of anti-friction material, suchas ceramic material or Teflon®, allow rotation of the tubular arm 64 inthe direction of a circular arrow 67, indicated in FIG. 3, so as toallow complete levelling of the slice 24 inside the cavity 28, therebyproviding the gripping and transportation means 60 with theself-levelling feature which forms part of this invention. Once theslice 24 is fully supported by and level inside the cavity 28 and theabsence of the vacuum 90 has caused separation of the hand 70 from thesaid slice, a further downward movement of the articulated arm 58results in raising of the hand 70 from the inner side of the slice 24,as can be seen in FIG. 8.

If we now examine FIGS. 9 to 12, it can be seen how the hand 70 may bedetached from the slice 24, releasing it entirely inside the cavity 28of the susceptor 26. In fact, in FIG. 9 it can be seen that, while thesaid absence of vacuum 90 keeps the hand 70 substantially detached fromthe slice 24, the arm 58 starts to move upwards in the direction of thebold arrow 104 until the hand 70 rests fully on the slice 24, as can beseen in FIG. 10, while remaining detached from the slice on account ofthe absence of vacuum 90 applied to the hand.

Subsequent raising of the articulated arm 58 in the direction of thearrow 104 causes raising of the hand 70 on the outer side, as can beseen in FIG. 11.

Finally, further raising of the arm 58 completely detaches and raisesthe hand 70 from the slice 24 and a retracting movement of the arm 58 inthe direction of the arrow 106 brings the gripping and transportationmeans 60 outside of the reaction chamber 22 (see FIG. 1).

FIGS. 13 to 16 depict the procedure with which the gripping means 60cause positioning of a hand 70 on a slice 24 seated in a cavity of thesusceptor 26 and FIGS. 17 to 20 depict raising and removal of the slice24 from the cavity 28 of the susceptor 26.

With reference in particular to FIGS. 13 to 16, it can be seen that thearticulated arm 58, with the forwards movement indicated by the arrow92, brings the hand 70 into alignment with the slice 24, whereas, withthe lowering movement indicated by the arrow 94, it causes the hand tomove towards the slice. As can be seen in FIG. 14, further lowering ofthe arm 58 brings the hand 70 into contact first with the inner side ofthe slice 24 and finally, as can be seen in FIG. 15, into contact withthe whole slice 24. The bushes 63 and 65, by allowing a rotation aboutthe axis of the tubular arm 64, also allow complete self-alignment ofthe hand 70 with the slice 24. The arm 58 may move downwards a littlefurther, as depicted in FIG. 16, causing a certain detachment of thehand 70 from the inner side of the slice 24, but this is of nosignificance.

With reference to FIG. 17, it can be seen how the articulated arm 58starts to move upwards again, as indicated by the arrow 104, while avacuum indicated by the arrow 90 is applied to the tubular arm 64,causing first the outer side of the slice 24 to adhere to the hand 70.Then, as indicated in FIG. 18, further raising of the articulated arm 58causes the hand 70 to adhere completely to the slice 24, while thevacuum 90 attaches the slice 24 to the hand 70.

Subsequent further raising of the arm 58 causes rotation of thearticulation means 62 about their pivot pin 98 until the screw 100 restson the pad 96, causing the outer side of the slice 24 to be detachedfrom the cavity 28 of the susceptor 26, as can be seen in FIG. 19,thereby avoiding any forced separation of the slice 24 from the cavity28, as could happen if it were attempted to detach the slice 24 keepingit parallel to the cavity 28. This avoids possible damage to the slice24 due to excessive forces applied by the hand 70 and possiblevibrations of the said tubular arm 64 due to a sudden release of theslice 24 from the cavity 28. Finally, as can be seen in FIG. 20, finalraising of the arm 58 in the direction of the arrow 104 completelydetaches the slice 24 from the cavity 28, while a retracting movement ofthe arm 28 in the direction of the arrow 106 brings the hand 70 togetherwith the slice 24 outside of the reaction chamber 22 (see FIG. 1).

It should be noted that, in order to avoid excessive deformationsresulting from warping of the slices 24 and/or offset small errors inalignment when the said slices are transported by the hand 70, means areprovided for adjusting the vacuum applied by the said hand 70. Inparticular, the vacuum must be kept at a maximum value while the hand 70starts to engage with the slices 24, but is then adjusted to a presetvalue when engagement of the hand 70 with the slices 24 has beencompleted.

The above description illustrates an example of embodiment of theinvention which is not to be regarded in any way as limiting theinvention, the covering scope of which will be defined only by theaccompanying claims. Therefore all those logically equivalent solutionswhich may occur to a person skilled in the art following reading of theabovementioned description must be regarded as being covered herein.

What is claimed is:
 1. Device for handling substrates of materialsproduced in epitaxial apparatuses or reactors such as slices ofsemiconductor materials, comprising: a reaction chamber (22), aninternal robot (30) for handling the substrates or slices (24) ofsemiconductor materials, a purging chamber (34) for passing the slices(24) through a cleaning atmosphere, a storage zone (36) containingcassettes (38, 40) which house, in a stacked arrangement, the slices(24) of semiconductor materials, an external robot (32) for transferringthe slices (24) from the storage zone (36) to the purging chamber (34),the internal robot (30) comprising a sealed chamber (56) which houses anarticulated arm (58) having a gripping means (60) at its external end,characterized in that the gripping means (60) of the internal robot (30)comprises at least one arm (64) which can be inserted into the reactionchamber (22) and terminating in a gripping tool or hand (70) forremoving a slice (24) of semiconductor material from the purging chamber(34) and transporting it, after passing through the sealed chamber (56),so as to be deposited in a recessed seat (28) of a disk-shaped susceptor(26) of the reaction chamber (22), and vice versa, from the recessedseat (28) to the purging chamber (34), where the hand (70) is designedto contact the slice (24) on its uppermost surface along a peripheralzone or chamfered edge (25) and the hand is adapted to grip the slice(24) by means of a vacuum effect, and where the gripping means (60)includes means for attaching it pivotally to the articulated arm (58) insuch a manner that when depositing the substrate in the recessed seat(28) the substrate is held inclined to the plane of the recessed seat(28) so as to touch the recessed seat (28) initially only with the sliceedge located furthest from the arm (64) of the gripping means (60)before then pivoting about said edge touching the seat to become fullyin contact therewith, and vice versa, when transporting a slice (24)from the reaction chamber (22) to the purging chamber (34), the slicegripped by the hand's vacuum effect is detached from the recessed seat(28) by first lifting the side of the slice nearest the arm (64) of thegripping means (60) and then detaching the substrate completely, andraising the substrate further whilst being held inclined to the plane ofthe recessed seat.
 2. Device for handling substrates according to claim1, characterized in that the arm (64) is tubular and hollow, beingconnected, on one side, by means of a flexible pipe (68) to a vacuumsource and, on the other side, to a circular seat (84) formed inside thehand (70) so as to apply a vacuum between a bottom side of the said band(70) and a slice (24) present underneath the hand (70).
 3. Device forhandling substrates according to claim 2, characterized in thatarticulation means (62) are arranged between the hollow tubular arm (64)and the articulated arm (58) of the internal robot (30), said meansallowing the hollow tubular arm (64) to be raised and lowered so as tobring the hand (70) above and below a plane defined by the articulatedarm (58).
 4. Device for handling substrates according to claim 3,characterized in that articulation means (62) are arranged between thehollow tubular arm (64) and the articulated arm (58) of the internalrobot (30), said means also allowing a rotation of the hollow tubulararm (64) about its longitudinal axis.
 5. Device for handling substratesaccording to claim 4, characterized in that the articulation means (62)comprise a support bearing (96) which is fixed to the articulated arm(58) and carries a rotating pin (98) about which the articulation means(62) rotate, and an adjusting screw (100) for fixing the permittedheights for raising and lowering of the hand (70) with respect to theplane of the articulated arm (58), so that the hand can rest in theradial direction on the disk-shaped susceptor (26) only with the frontpart, only with the rear part or perfectly level with the said susceptor(26).
 6. Device for handling substrates according to claim 5,characterized in that the articulation means (62) also comprise, aroundthe hollow tubular arm (64), anti-fiction bushes (63, 65) for allowingalignment of the said hand (70), in a direction perpendicular to theradius of the disk-shaped susceptor (26).
 7. Device for handlingsubstrates according to claim 6, characterized in that the hand (70) isin the form of a disk with a diameter greater than the diameter of theslice (24) to be handled and has a bottom part (74), facing the slice(24), provided with a recessed seat which engages only with an externalperipheral rim (25) of the said slice (24).
 8. Device for handlingsubstrates according to claim 7, characterized in that the seat ispresent on a bottom part (74) of the hand (70) and is provided with aplurality of peripheral holes (86) connected to a chamber (84) insidethe said hand (70) which, in turn, is connected to the hollow tubulararm (64) so as to apply a vacuum between the slice (24) and the hand(70).
 9. Device for handling substrates according to claim 8,characterized in that the peripheral holes (86) are concentrated mainlywhere the greatest losses in vacuum are envisaged.
 10. Device forhandling substrates as recited in any one of claims 1-9, characterizedin that a laser telemeter is used to measure a distance between a laseremitter and the disk-shaped susceptor (26) of the reaction chamber (22),in question, producing an analogue signal proportional to the saiddistance, where said telemeter detects defects in the level arrangementof the susceptor (26) as well as defects in the parallel positioning ofthe susceptor (26) with respect to the reaction chamber (22).
 11. Devicefor handling substrates according to claim 10, characterized in that anotch formed in the external rim of the susceptor (26) is used as anangular reference point which can be detected by the laser telemeter andthe recessed seats (28) for the slices (24) are counted starting fromthis notch.
 12. Method for placing a slice (24) in a recessed seat (28)of a disk-shaped susceptor (26), present in a reaction chamber (22), bymeans of a hand (70) of a device according to any one of claims 1-9,characterized in that a slice (24), which is made to adhere to the hand(70) by means of a vacuum, enters into the reaction chamber (22) in theraised position, is transported to above one of the recessed seats (28)of the disk-shaped susceptor (26), is lowered so as to be placed ontothe said seat (28), remaining inclined forwards so as to touch therecessed seat (28) initially only with the slice edge located farthestfrom the arm (64) of the gripping means (60), and then, after removal ofthe vacuum which keeps the slice (24) attached to the hand (70), isfurther lowered, detaching the hand (70) from the slice (24), and thenthe hand (70) is raised again, being detached entirely from the slice(24), and finally is retracted, leaving the reaction chamber (22). 13.Method for removing a slice (24) from a recessed seat (28) of adisk-shaped susceptor (26), present in a reaction chamber (22), by meansof a hand (70) of a device according to any one of claims 1-9,characterized in that the hand (70) enters into the reaction chamber(22) in the raised position, is transported to above a slice (24) housedin one of the recessed seats (28) of the disk-shaped susceptor (26), islowered until it touches the slice (24), first at the edge locatedfarthest from the arm (64) of the gripping means (60) and then over theentire circumference of the slice (24) and then, after touching theslice over the entire circumference, applies a vacuum so as to cause theslice (24) to adhere with its edge (25) onto the hand (70) and thenstarts to move up again; detaching the slice (24) from the recessed seat(28), first at the edge located nearest the arm (64) of the grippingmeans (60) and then over the entire surface of the slice (24), andfinally, after the slice (24) has been raised completely from therecessed seat (28) of the susceptor (26), transports it outside thereaction chamber (22).
 14. Method according to claim 13, characterizedin that, in order to avoid excessive deformations of the slices (24) dueto warping, a vacuum is applied to the hand (70), said vacuum being at amaximum at the start of engagement of the slices (24) by the said hand(70), when the slices (24) are not fully in contact with the hand (70),but subsequently means for adjusting the vacuum reduce the said vacuumto a minimum value sufficient to maintain adhesion between slices (24)and hand (70) without causing substantial deformation of the slices(24).
 15. The method according to claim 12, characterized in that, inorder to avoid excessive deformations of the slices (24) due to warping,a vacuum is applied to the hand (70), said vacuum being at a maximum atthe start of engagement of the slices (24) by the said band (70), whenthe slices (24) are not fully in contact with the band (70), butsubsequently means for adjusting the vacuum reduce the said vacuum to aminimum value sufficient to maintain adhesion between slices (24) andhand (70) without causing substantial deformation of the slices (24).